GB2073670A - Inking control system for a printing machine - Google Patents

Abstract

An ink zone remote adjustment system for a printing machine comprises ductor knife support elements acting on ductor knife and equipped with actuating systems (1) comprising adjustment drives (2) and position measurement transmitters (3). The adjustment system further comprises a control section, which comprises one or more converter systems, a control system (9) operating in the actuation process for assimilating the discontinuous path of the positions of the support elements to the continuous function of the ductor knife flexion line when predetermined limiting values are exceeded, and a summating unit (11). The control system (9) comprises a manually actuatable triggering unit, a sequence control starting in a non- repetitive cycle from an end one of the actuating systems (1), interrogating the position measurement transmitters (3) and switching on the adjustment drives (2), a difference former which compares the difference between two adjacent actuating systems (2), and a computing unit which computes the actuation values for the adjustment drives (2) of adjacent actuating systems and of those adjoining actuating systems on both sides. <IMAGE>

Description

SPECIFICATION Inking control system for a printing machine The present invention relates to an inking control system for a printing machine.

Ink zone remote adjustment systems are used in multi-colour printing machines for the remote control of the individual inking devices, especially the ink metering devices. Ink metering devices consist of an ink duct comprising a ductor blade or knife acted on by actuating systems consisting of an adjustment drive and a position measurement transmitter. The actuation values for the actuating systems are obtained from a densitometric evaluation of the printed sheets.

Ink metering devices are known (US-PS 3 835 777), which consist of one or more conversion systems for converting the densitometer values into actuation values, a control system operating in the actuation process for assimilating the discontinuous path of the positions of the ductor knife support elements to the continuous function of the ductor knife flexion line when predetermined limiting values are exceeded.

The assimilation is carried out over the entire range; the algorithm of the assimilating picks up all the actual positions, arranged them according to an ascending or descending order of all differences and smooths out all discontinuities in the correct sequence. In this case, a multiple processing of a discontinuity and a multiple traversing of the assimilation system- is carried out. The assimilation traversal is carried out at each change.

A disadvantage of this method is that, due to the smoothing algorithm, the assimilation can only be effected by a computer and the expenditure (preparation of an order table, multiple, traversing, traversal at each change) in carrying out the method is very high. As a consequence of the processing algorithm, which processes only two values and assimiiates one or two values, the accuracy achieved is not very high. The theoretically achieved degree of accuracy of the processing bears no relationship to the practically achieved accuracy due to the fact that no account is taken of the function of the knife flexion line.

There is accordingly a need for an inking control system of simple construction and low constructional and minimal processing costs, the system allowing assimilation to be carried out in a single processing cycle.

According to the present invention there is provided an inking control system for a printing machine, comprising a row of support elements acting on a continuous flexible ductor blade, a respective drive operable to adjust the position of each support element, a respective measuring device for measuring a parameter associated with the position of each support element and providing a signal having a magnitude indicative of the parameter measurement, and drive control means for controlling the drives to so adjust the positions of the support elements as to assimilate the course of the row to the line of flexion of the blade if and when such course deviates from such line by more than a predetermined amount, the drive control means comprising interrogation means actuable by trigger means to interrogate the measuring devices in a single continuous sequence, difference determining means for determining whether a difference between the magnitudes of the signals of interrogated measuring devices associated with any pair of support elements exceeds a threshold value, and calculating means responsive to determination of a difference exceeding the threshold value to calculate adjustment magnitudes for use in adjustment of the relevant pair of support elements and of the support elements adjoining that pair by way of the respective drives.

In an embodiment of the invention, the inking control system expediently comprises support elements acting on an undivided ductor blade, actuating systems consisting of adjustment drives and position measurement transmitters, and a control section, which comprises one or more conversion systems, a control system operating in the actuating process for assimilating the discontinuous cpurse of the positions of the support elements to the continuous function of the ductor blade flexion line when predetermined limiting values are exceeded, and a summation unit.The control system expediently comprises a manually actuated triggering unit, a sequence control which starts in a non-repetitive cycle from an end one of the actuation systems, interrogates the position measuring transmitters and switches on the adjustment drives, a difference former which compares the difference between two adjacent actuation systems, and a computing means which calculate actuating commands for the adjustment drives of adjacent actuating systems and those adjoining on either side.

A common reference position is preferably associated with the position measurement transmitters.

The computing means is preferably adapted to carry out assimilation in sections according to a linear function, the increment of which is dependent upon the difference between two adjacent actuation systems. Alternatively, the computing means may be adapted to carry out the assimilation according to a non-linear function, either in sections or as a whole. Such non-linear function is preferably the Newtonian approximation polynomial.

The discontinuity in the course of the positions of the support elements and the point of flection of the approximation function are preferably associated with one and the same location.

An embodiment of the present invention will now be more particularly described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a schematic block diagram of an ink zone remote adjustment system according to the said embodiment, Fig. 2 is a schematic block diagram pf a control system in the adjustment system, and Fig. 3 is a schematic illustration of ductor knife support elements of the adjustment system, illustrating the principle of the control of adjustment of the support elements.

Referring now to the drawings, there is shown in Fig. 1 an ink zone remote adjustment system for a printing machine. The adjustment system comprises a plurality of actuating systems 1 corresponding in number to a plurality of support elements (not shown in Fig, 1) for a ductor knife (not shown). Each-actuating system 1 comprises an adjustment drive 2, which varies the position of the ductor knife support element and a position measurement transmitter 3, which picks up the position of the ductor knife support element and/or of the ductor knife. The output from the adjustment drive 2 is connected with the position measurement transmitter 3 and with further known functional groups of a printed image generating means 4 of the printing machine.

Among the functional groups of the image generating means are such printing mechanisms as inking and humidifying devices and offset, plate and printing cylinders. A finished print 5 is provided at the output from the functional groups of the generating means 4. The finished print is densitometrically surveyed, and densitometer readings being converted in a converting system 6 into measured values A and fed via a conductor system 7 to a control system 9. Measured values B present at the output of the position measurement transmitter 3 are fed via a conducting system 8 to the control system 9. The control system 9 supplies actuation values, which pass through a conducting system 10 and a summating unit 11 to the actuating systems 1.

The summating unit 11 is connected with a further converter system 12, which receives target densitometer values at its input.

The group Comprising the functional groups, converter system 12, summating unit 11 and actuating system 1 is present in multiplied form corresponding to the number of ductor knife support elements. The range comprising the functional groups, printed image generator 4 and the converter system 6 is present in multiplied form according to the circumstances of the printing machine. These two groups are illustrated only in simplified form in Fig. 1. By contrast, only one control system 9 is present in the ink zone remote adjustment system, but is depicted with a number of signal lines for measured values A or measured values B and for actuation values corresponding to the number of the support elements and to the form of the group comprising the functional groups of the printed image generator 4 and first converter system 6.

The construction of the control system 9 is shown in Fig. 2. A manually actuated triggering unit 13 is connected with a sequence control 14, which receives at its input side the measured values B via the conductor system 8 or measured values A via the first conductor system 7 and supplies at its output side the actuation values via the conductor system 10. To carry out the necessary operations, further connections exist between the sequence control 14, a difference former 1 5 and a computing unit 16.

Fig. 3 shows the portion of an ink zone remote adjustment system comprising the ductor knife support elements 17.1 to 17.6, their starting positions 17.1' to 17.6' before assimilation, and their positions 1 7.2" to 17.5" after assimilation.

A common reference position for all the support elements 17.1 to 17.6 is denoted by 18.

In operation, the converter system 12, by surveying proof prints, sample sheets or separate prints and by converting technical printing characteristic data such as colour density into electrical signals, supplies values which pass via the summatingrunit 11 to the actuating systems 1 and there effect the adjustment of the support elements via adjustment drives 2. It is also possible for the operator to directly input values, based on observations and experience, into the summating unit 11. The change in position of a support element or of the ductor knife is detected by the position transmitter 3 of the respective actuating'system 1 , which transmitter supplies the measure values B.Such changes in position of the support elements influence, via the functional groups of the printed image generator 4, the printed image 5, and can thus be surveyed by means of the converter system 6 and converted into the measured values A.

The measured values A or the measured values B are applied to the control system 9. This control system 9 has the task of assimilating the discontinuous course of the positions of the support elements to the continuous function of the ductor knife flexion line when specific limiting values are exceeded. This assimilating has the objective of avoiding such differences in position between ductor knife and support elements as might cause the ductor knife to lift off the support elements.

For this purpose there is carried out in the control system 9 a computation of actuation values for the actuating means in accordance with pre-input interrelationships and by means of the measured values A or B. The actuation values for the assimilation pass, via the summating unit 11, to the actuating system 1, which causes a' corresponding adjustment in the ink zone remote adjustment system. The control system 9 is triggered by a command from the triggering unit 13, which is manually actuated during the adjustment process, to the sequence control 14.

The sequence control 14 then commences a nonrepetitive cycle at one of the two extreme actuation systems, which cycle continues in the correct sequence continuously to the opposite extreme system. In this process, two adjacent measured values A or two adjacent measured values B are interrogated and are checked in the difference former 15, after subtraction, to see whether a specific limiting value has been exceeded. If the- limiting value has not been exceeded, the sequence control 14 interrogates the next two adjacent measured values A or measured values B.

If, however, the limiting value is exceeded, the measured values A or measured values B of further actuating systems adjoining on each side are interrogated and are processed in the computing unit 1 6. By means of the sequence control 14, the actuation values established in the computing unit 1 6 are output via the summating unit 11 and the corresponding actuating systems 1 are switched on for correcting the positions of a plurality of support elements situated on either side of the support elements associated with the exceeded limited value.

The task of the control system 9 may also be carried out by an appropriately programmed microcomputer. Moreover, the use of a microcomputer affords the possibility of taking over the functions of the converter systems 6 and 12.

Fig. 3 illustrates the principle of the assimilation of the support elements to the ductor knife line of flexion.

As already mentioned, the support elements 17.1 to 17.6 have a common reference position 1 8. Relative to this reference position 18, the ductor knife support elements 17.1 to 17.6 have the same position 17.1' to 17.6' before the assimilation is carried out. When the adjacent support elements 17.3 and 17.4 are compared, the difference A between the positions 17.3' and 1 7.4' of the support elements 17.3 and 1 7.4 is found to exceed the predetermined limiting value Amax and an assimilating operation is necessary.

This is carried out in sections by a linear function (straight line), the slope of which, as shown in Fig. 3, is dependent upon the difference A of the adjacent support elements 1 7.3 and 17.4.

After the above-described functions, appropriate adjustment of the positions of the support elements 17.3 and 1 7.4 is carried out and the support elements 17.2 and 17.5, adjoining the elements 17.3 and 17.4 at both sides, are adjusted into new positions 1 7.2" to 1 7.5".

In the example of Fig. 3, the assimilating has been carried out in sections by means of a linear function. It is, however, also possible to use a nonlinear function for the assimilating. This has the advantage of allowing the assimilation to be carried out either in sections or over the entire range. A function suitable for such tasks is the Newtonian approximation polynomial, the support positions of which takes account of all or only some of the positions of the support elements.

Claims (10)

1. An inking control system for a printing machine, comprising a row of support elements acting on a continuous flexible ductor blade, a respective drive operable to adjust the position of each support element, a respective measuring device for measuring a parameter associated with the position of each support element and providing a signal having a magnitude indicative of the parameter measurement, and drive control means for controlling the drives to so adjust the positions of the support elements as to assimilate the course of the row to the line of flexion of the blade if and when such course deviates from such line by more than a predetermined amount, the drive control means comprising interrogation means actuable by trigger means to interrogate the measuring devices in a single continuous sequence, difference determining means for determining whether a difference between the magnitudes of the signals of interrogated measuring devices associated with any pair of support elements exceeds a threshold value, and calculating means responsive to determination of a difference exceeding the threshold value to calculate adjustment magnitudes for use in adjustment of the relevant pair of support elements and of the support elements adjoining that pair by way of the respective drives.

2. A system as claimed in claim 1, comprising converter means for converting parameter measurements into corresponding signal magnitudes.

3. A system as claimed in either claim 1 or claim 2, comprising summation means for combining such calculated adjustment magnitudes with predetermined adjustment magnitudes.

4. A system as claimed in any one of the preceding claims, wherein the measuring devices are adapted to provide signals having magnitudes indicative of the positions of the support elements themselves.

5. A system as claimed in claim 4, wherein the measuring devices are adapted to determine said positions with respect to a reference position common to all of the support elements.

6. A system as claimed in any one of the preceding claims, the calculating means being adapted to calculate adjustment magnitudes for adjustment of the appropriate support elements by sections in accordance with a linear function providing an increment dependent on the magnitude of said difference exceeding the threshold value.

7. A system as claimed in any one of claims 1 to 5, the calculating means being adapted to calculate adjustment magnitudes for adjustment of the appropriate support elements in accordance with a non-linear function.

8. A system as claimed in claim 7, the nonlinear function being the Newtonian approximation polynomial.

9. A system as claimed in either claim 7 or claim 8, the calculating means being adapted to so calculate the adjustment magnitudes that the point of inflection of the function coincides with the magnitude required for adjustment of the two support elements associated with the measuring devices providing said signal magnitude difference exceeding the threshold value.

10. An inking control system for a printing machine, the system being substantially as hereinbefore described with reference to the accompanying drawings.